1. Field of the Invention
The present invention relates to the field of one-time programming memory cells (OTP) and more specifically to the forming of a one-time programming memory in an integrated circuit.
2. Discussion of the Related Art
Conventionally, integrated circuit one-time programming memories are of EPROM type and thus require specific programming circuits which are not compatible with standard technologies of manufacturing of the MOS transistors used in integrated circuits. There also are one-time programming memories formed by EEPROMs and non-erasable flash memories.
Another category of one-time programming memories is formed of fuse or anti-fuse memories. Such memories include memories formed of a polysilicon bar or track which is submitted to a very high current to physically deteriorate the polysilicon and open the circuit. Such one-time programming memory cells require very high currents (on the order of one hundred milliamperes). This considerably limits their use. Further, the programming performed on a fuse-type cell is optically visible, which is detrimental to the security of a binary code embedded in an integrated circuit and masked in a one-time programming memory.
A similar disadvantage exists with memories of EPROM or EEPROM type, that is, a detection of the state of the storage cells is possible by means of an electronic scanning microscope which can detect the difference of accumulated charges in the floating gate transistors of such memories.
The present invention aims at providing a novel one-time programming memory structure which overcomes the disadvantages of known structures.
The present invention more specifically aims at providing the forming of an integrated circuit memory cell which requires no additional manufacturing step with respect to the steps implemented to manufacture MOS transistors in conventional technologies.
The present invention also aims at improving the security of an embedded code by means of a one-time programming memory cell.
The present invention also aims at providing a low-cost memory cell.
The present invention also aims at providing a one-time programming memory cell.